AP Chemistry Flashcards: Complete 9-Unit Course Review
Review all nine AP Chemistry units with 450 cards covering concepts, models, equations, calculation setup, and laboratory reasoning.
Про цю колоду
Review AP® Chemistry through 450 independently written English flashcards arranged in the course's nine-unit sequence. The deck moves from atomic structure and compound structure through properties of substances and mixtures, reactions, kinetics, thermochemistry, equilibrium, acids and bases, and thermodynamics and electrochemistry. Prerequisites come before dependent models and calculations.
What the cards practice
The cards use five recall paths: concept to explanation; model or representation to interpretation; equation to meaning and use; short setup to a result with units and reasoning; and laboratory observation to a chemical conclusion. They cover definitions, relationships, conditions, contrasts, particle and energy models, focused calculation steps, measurements, errors, and visible changes.
Selected reverse and contrast prompts appear only when the reverse direction has one clear standalone target. The deck excludes mechanical permutations, graph-dependent prompts that require a missing figure, copied test formats, long multipart derivations, and visual recall tied to third-party figures. The review scheduler handles long-term spacing after installation.
See the official AP Chemistry course page for College Board's current course requirements.
The Common knowledge · CC0 1.0 label applies only to the independently written prompts, answers, examples, organization, metadata, and inherited original cover, to the extent applicable rights exist. It does not claim ownership of scientific facts or equations.
This is an independent, unofficial study aid. It is not affiliated with, endorsed by, sponsored by, or official material from College Board or the AP Program. AP® is a trademark registered by the College Board, which is not affiliated with, and does not endorse, this product. No College Board examination questions, answer choices, scoring materials, curriculum text, logos, or trade dress were copied.
Картки в цій колоді
Картка 1
Питання
What does one mole count?
Відповідь
Exactly 6.02214076 × 10^23 representative particles.
Картка 2
Питання
What does a peak in an element's mass spectrum represent?
Відповідь
An isotope with a particular mass-to-charge ratio; for singly charged monatomic ions, the position tracks isotopic mass.
Картка 3
Питання
What does an empirical formula show?
Відповідь
The lowest whole-number ratio of the elements' atoms in a compound.
Картка 4
Питання
How does a mixture differ from a pure substance at the particle level?
Відповідь
A mixture contains chemically distinct representative units in variable proportions; a pure substance contains one element or compound with fixed composition. Different isotopes do not make an elemental sample a mixture.
Картка 5
Питання
Which particles make up an atom's nucleus?
Відповідь
Protons and neutrons. Electrons occupy the space outside the nucleus.
Картка 6
Питання
What does a larger binding energy on a PES spectrum mean?
Відповідь
More energy is required to remove that electron, so it is held more strongly by the nucleus.
Картка 7
Питання
How does atomic radius generally change across a period and down a group?
Відповідь
It decreases from left to right as effective nuclear charge rises, and it increases down a group as additional electron shells increase distance and shielding.
Картка 8
Питання
What typical ion charge do Group 1 metals form?
Відповідь
+1, by losing their one valence electron.
Картка 9
Питання
How do you convert moles to particles?
Відповідь
Multiply by Avogadro's number: particles = moles × 6.022 × 10^23 mol^-1.
Картка 10
Питання
How is average atomic mass estimated from isotope data?
Відповідь
Add each isotopic mass multiplied by its fractional abundance.
Картка 11
Питання
How is an element's mass percent in a compound calculated?
Відповідь
Divide the mass contributed by that element by the compound's molar mass, then multiply by 100%.
Картка 12
Питання
How can measured elemental composition reveal a sample's purity?
Відповідь
Compare the measured mass fraction with the fraction expected for the pure compound; a mismatch indicates another component.
Картка 13
Питання
How do you build a ground-state electron configuration with the Aufbau principle?
Відповідь
For ordinary ground states, move through the periodic table in atomic-number order, filling each s, p, d, or f block as it appears. The subshell capacities are s², p⁶, d¹⁰, and f¹⁴. For example, Br is [Ar] 4s² 3d¹⁰ 4p⁵.
Картка 14
Питання
What does the relative area or height of an ideal PES peak indicate?
Відповідь
The relative number of electrons in the corresponding subshell.
Картка 15
Питання
How does first ionization energy generally change across a period and down a group?
Відповідь
It increases from left to right as effective nuclear charge rises, and it decreases down a group as distance and shielding make a valence electron easier to remove.
Картка 16
Питання
Why do elements in the same group form similar compounds?
Відповідь
Their ground-state valence patterns repeat, including which outer subshells are full or partly full. That leads to similar bonding and typical ion charges.
Картка 17
Питання
How do you convert a sample's mass to moles?
Відповідь
Divide its mass by its molar mass: n = m/M.
Картка 18
Питання
Which mass-spectrum interpretation lies outside the usual single-element model used in this deck?
Відповідь
Assigning peaks in mixtures or peaks from multiply charged or polyatomic species; the standard model uses singly charged monatomic ions of one element.
Картка 19
Питання
What does the law of definite proportions state?
Відповідь
Every pure sample of a given compound has the same element mass ratios.
Картка 20
Питання
Why can two samples of the same mixture have different compositions?
Відповідь
Mixture components are physically combined, so their relative amounts are not fixed by a chemical formula.
Картка 21
Питання
How does Coulomb's law connect charge and separation to attraction?
Відповідь
Attraction grows with the magnitude of the charge product and decreases with the square of the separation distance.
Картка 22
Питання
Which PES electrons usually appear at the highest binding energy?
Відповідь
Core electrons closest to the nucleus, because they feel the strongest nuclear attraction.
Картка 23
Питання
How does electron affinity generally change across a period and down a group?
Відповідь
Electron gain generally becomes more favorable from left to right across a period and less favorable down a group as distance and shielding increase. Stable subshell patterns create substantial exceptions.
Картка 24
Питання
Why are alkali metals generally more reactive down the group?
Відповідь
Their valence electron is farther from the nucleus and easier to remove.
Картка 25
Питання
How many moles are in 18.0 g of H₂O?
Відповідь
About 0.999 mol. Use 18.0 g ÷ 18.02 g mol^-1.
Картка 26
Питання
An element is 75% isotope 10 and 25% isotope 11; what is its average atomic mass?
Відповідь
10.25 u. Calculate (0.75 × 10) + (0.25 × 11).
Картка 27
Питання
A compound is 40.0% C, 6.7% H, and 53.3% O by mass; what is its empirical formula?
Відповідь
CH₂O. For a 100 g sample, convert each mass to moles and divide by the smallest amount.
Картка 28
Питання
A 10.0 g impure sample contains 8.5 g of the target compound; what is its mass-percent purity?
Відповідь
85%. Calculate (8.5 g ÷ 10.0 g) × 100%.
Картка 29
Питання
Which electrons are removed first when a transition metal forms a cation?
Відповідь
Electrons in the occupied orbital with the highest principal quantum number: 4s before 3d. For example, Fe²⁺ is [Ar] 3d⁶.
Картка 30
Питання
A PES spectrum has peaks proportional to 2, 2, and 6 electrons; which configuration fits?
Відповідь
1s² 2s² 2p⁶, the configuration of Ne.
Картка 31
Питання
How does electronegativity generally change across a period and down a group?
Відповідь
It increases from left to right across a period and decreases down a group as atomic size and shielding increase.
Картка 32
Питання
What empirical formula results from Al³⁺ and O²⁻?
Відповідь
Al₂O₃, because two Al³⁺ ions balance three O²⁻ ions.
Картка 33
Питання
How does a particle's mass in atomic mass units relate to its molar mass?
Відповідь
The numerical value is the same: a molecular or formula-unit mass of x u corresponds to a molar mass of x g mol^-1.
Картка 34
Питання
What does the tallest isotope peak usually indicate in a simple mass spectrum?
Відповідь
The most abundant isotope, assuming comparable detection response and singly charged ions.
Картка 35
Питання
How much oxygen is present in 25.0 g of a compound that is 32.0% oxygen by mass?
Відповідь
8.00 g O. Multiply 25.0 g by 0.320.
Картка 36
Питання
What does a particle diagram with two unbonded species in changing ratios represent?
Відповідь
A mixture, because more than one particle type is present and the ratio is not fixed in a formula unit.
Картка 37
Питання
What distinguishes valence electrons from core electrons?
Відповідь
Valence electrons are available for bonding or ion formation; main-group valence electrons occupy the outermost shell, while transition metals may also use (n−1)d electrons. Core electrons mainly shield nuclear charge.
Картка 38
Питання
Why can PES peak groups reveal an atom's occupied subshells?
Відповідь
Electrons in different subshells require distinct removal energies, producing separate binding-energy groups.
Картка 39
Питання
How do ion radii compare with neutral atoms and within an isoelectronic series?
Відповідь
Cations are smaller than their neutral atoms, while anions are larger. Among species with the same electron count, more protons pull the electrons closer and produce the smaller radius.
Картка 40
Питання
What formula is expected for a compound between a Group 2 metal M and a Group 17 nonmetal X?
Відповідь
MX₂, because M forms M²⁺ and X forms X⁻.
Картка 41
Питання
When is a covalent bond considered nonpolar?
Відповідь
When the bonded atoms have identical or very similar electronegativities, so the shared electron density is distributed approximately evenly.
Картка 42
Питання
Why does a bonded pair of atoms have an equilibrium bond length?
Відповідь
At that separation, attractive and repulsive interactions balance at minimum potential energy.
Картка 43
Питання
How are particles arranged in an ionic solid?
Відповідь
Cations and anions occupy a repeating three-dimensional lattice held by electrostatic attraction.
Картка 44
Питання
What model explains bonding in a metal?
Відповідь
Positive metal cores are held together by attraction to mobile, delocalized valence electrons.
Картка 45
Питання
How do you construct a Lewis diagram?
Відповідь
Count total valence electrons, adding electrons for a negative charge and subtracting them for a positive charge. Choose a skeleton, connect atoms with single bonds, complete terminal duets or octets, and place remaining electrons on the central atom. Add multiple bonds if needed, then check the electron total and formal charges.
Картка 46
Питання
What does resonance mean in a molecule or ion?
Відповідь
Resonance uses two or more valid Lewis diagrams with the same atom arrangement but different electron placement. The actual electron distribution is a hybrid; equivalent contributors have equal weight.
Картка 47
Питання
What determines molecular shape in VSEPR theory?
Відповідь
Electron domains around the central atom arrange to minimize repulsions.
Картка 48
Питання
How does an ionic bond differ from a covalent bond?
Відповідь
Ionic bonding is attraction among oppositely charged ions in an extended structure; covalent bonding uses shared electron density between atoms.
Картка 49
Питання
What happens to potential energy when bonded atoms are pushed much closer than equilibrium?
Відповідь
Potential energy rises sharply because nucleus–nucleus and electron–electron repulsions dominate.
Картка 50
Питання
Why are many ionic solids brittle?
Відповідь
A shifted lattice can align like charges, creating strong repulsion that splits the crystal.
Картка 51
Питання
What molecular shapes arise from two electron domains with no lone pairs and from three domains with zero or one lone pair?
Відповідь
Two bonding domains give linear with a 180° angle. Three domains with no lone pairs give trigonal planar with 120° angles; replacing one bond with a lone pair gives bent with an angle slightly below 120°.
Картка 52
Питання
Why are metals electrically conductive as solids?
Відповідь
Their delocalized electrons can move through the solid when an electric field is applied.
Картка 53
Питання
How is formal charge calculated for an atom in a Lewis diagram?
Відповідь
Formal charge = valence electrons − nonbonding electrons − half the bonding electrons.
Картка 54
Питання
Why can't electronegativity difference alone classify a bond as ionic or covalent?
Відповідь
Bonding lies on a continuum. A larger difference means more ionic character, but the element types and especially the compound's properties give the best classification.
Картка 55
Питання
Which shapes and bond-angle trends arise as lone pairs replace bonds in four electron domains?
Відповідь
Four bonds give tetrahedral with ideal 109.5° angles. One lone pair gives trigonal pyramidal with smaller angles; two lone pairs give bent with typically smaller angles again because lone pairs repel more strongly than bonding pairs.
Картка 56
Питання
What feature of a potential-energy curve represents bond dissociation energy?
Відповідь
The energy difference from the curve's minimum to the separated-atoms limit.
Картка 57
Питання
When does an ionic compound conduct electricity?
Відповідь
When molten or dissolved so its ions can move; not as a rigid solid lattice.
Картка 58
Питання
What is a substitutional alloy?
Відповідь
An alloy in which atoms of a similar size replace some host-metal atoms in the lattice.
Картка 59
Питання
How do two, three, and four electron domains map to hybridization?
Відповідь
Two domains map to sp, three to sp², and four to sp³, with ideal angles of 180°, 120°, and 109.5°. Hybridization involving d orbitals is outside this deck’s scope.
Картка 60
Питання
What usually makes one resonance contributor more favorable than another?
Відповідь
Smaller formal-charge magnitudes, appropriate negative charge on more electronegative atoms, and complete valence shells where applicable.
Картка 61
Питання
How many sigma and pi bonds are in single, double, and triple bonds?
Відповідь
A single bond has one sigma bond; a double has one sigma and one pi bond; a triple has one sigma and two pi bonds. Head-on sigma overlap is stronger than side-by-side pi overlap.
Картка 62
Питання
Why is a polar covalent bond polar?
Відповідь
Unequal electronegativity creates an uneven sharing of electron density and partial charges.
Картка 63
Питання
Which molecular shapes arise as lone pairs replace bonds in five electron domains?
Відповідь
Five bonds give trigonal bipyramidal; four bonds and one lone pair give seesaw; three bonds and two lone pairs give T-shaped; two bonds and three lone pairs give linear.
Картка 64
Питання
How do ionic charge and ionic radius affect attraction between ions?
Відповідь
Larger charge magnitudes and smaller ionic radii produce stronger attraction because the charge product increases and the ion centers are closer.
Картка 65
Питання
Why do ionic solids often have high melting points?
Відповідь
Many strong Coulombic attractions throughout the lattice must be overcome to free the ions.
Картка 66
Питання
What is an interstitial alloy?
Відповідь
A smaller atom occupies holes between host-metal atoms, often making lattice layers harder to slide.
Картка 67
Питання
What shape has six bonding domains and no lone pairs on the central atom?
Відповідь
Octahedral.
Картка 68
Питання
Which elements commonly form incomplete octets in stable Lewis diagrams?
Відповідь
Hydrogen forms a duet, and electron-deficient central atoms such as boron or beryllium can have fewer than eight electrons.
Картка 69
Питання
How do bond order and atomic size affect covalent bond length and strength?
Відповідь
Within a comparable bond family, higher bond order gives shorter, stronger bonds. Larger bonded atoms generally give longer bonds, which are often weaker because their orbitals overlap less effectively.
Картка 70
Питання
What bonding model best fits a sample that is malleable and conducts as a solid?
Відповідь
Metallic bonding with mobile, delocalized electrons and nondirectional attractions.
Картка 71
Питання
What shape has six electron domains, five bonds, and one lone pair?
Відповідь
Square pyramidal.
Картка 72
Питання
Which lattice should have stronger attractions: MgO or NaCl, assuming similar separations?
Відповідь
MgO, because the charge product for Mg²⁺ and O²⁻ is larger than for Na⁺ and Cl⁻.
Картка 73
Питання
Why are pure metals often malleable?
Відповідь
Metal cores can shift while the mobile electron sea maintains nondirectional attraction instead of exposing fixed like-charge planes.
Картка 74
Питання
What is the best Lewis structure for CO₂?
Відповідь
O=C=O, with two lone pairs on each oxygen and no formal charges.
Картка 75
Питання
What shape has six electron domains, four bonds, and two opposite lone pairs?
Відповідь
Square planar.
Картка 76
Питання
What limitation does an odd total number of valence electrons create for a Lewis diagram?
Відповідь
At least one electron must remain unpaired, so not every atom can have a complete paired-electron octet.
Картка 77
Питання
What does a higher bond order do to a bond's potential-energy curve?
Відповідь
It generally places the minimum at a shorter internuclear distance and makes the well deeper, corresponding to a shorter bond and a larger bond-dissociation energy.
Картка 78
Питання
When can a carbon–carbon double bond produce geometric isomers?
Відповідь
When each carbon has two different substituents. The pi bond restricts rotation, so distinct spatial arrangements can persist.
Картка 79
Питання
When may a third-period central atom exceed an octet in a Lewis diagram?
Відповідь
When the valid electron count and lower formal charges favor an expanded valence shell, as in species such as SF₆.
Картка 80
Питання
How do you decide whether a molecule with polar bonds is polar overall?
Відповідь
Add the bond-dipole vectors using the molecular shape; symmetry may cancel them, while an asymmetric arrangement leaves a net dipole.
Картка 81
Питання
Which interparticle forces act between all atoms and molecules?
Відповідь
London dispersion forces, caused by temporary and induced dipoles.
Картка 82
Питання
What four broad solid types does this deck compare?
Відповідь
Ionic, metallic, molecular, and covalent-network solids.
Картка 83
Питання
How do gas particles differ from liquid particles?
Відповідь
Gas particles are much farther apart and move independently; liquid particles stay close but can move past one another.
Картка 84
Питання
What relationship connects pressure, volume, amount, and temperature for an ideal gas?
Відповідь
PV = nRT, with absolute temperature in kelvins and units consistent with R.
Картка 85
Питання
What does temperature measure in kinetic molecular theory?
Відповідь
The particles' average translational kinetic energy.
Картка 86
Питання
What two ideal-gas assumptions fail most clearly for real gases?
Відповідь
Particles have nonzero volume and experience intermolecular attractions.
Картка 87
Питання
How is molarity defined?
Відповідь
Moles of solute per liter of solution: M = n/V.
Картка 88
Питання
What must a correct particulate diagram of NaCl(aq) show?
Відповідь
Separated Na⁺ and Cl⁻ ions in a 1:1 ratio, each surrounded by oriented water molecules.
Картка 89
Питання
Which separation method removes an insoluble solid from a liquid?
Відповідь
Filtration: the solid stays as residue while the liquid passes as filtrate.
Картка 90
Питання
What does “like dissolves like” mean at the particle level?
Відповідь
A solute tends to dissolve when new solute–solvent attractions can compete with the attractions disrupted in the pure substances.
Картка 91
Питання
What happens when matter absorbs electromagnetic radiation?
Відповідь
Its particles move to an allowed higher-energy state when the photon energy matches the energy gap.
Картка 92
Питання
Which equations connect photon energy, frequency, and wavelength?
Відповідь
E = hν and c = λν.
Картка 93
Питання
What is the Beer–Lambert law?
Відповідь
A = εbc: absorbance equals molar absorptivity at the chosen wavelength times path length times concentration.
Картка 94
Питання
What molecular features generally strengthen London dispersion forces?
Відповідь
More electrons and a more polarizable cloud strengthen temporary dipoles; greater contact area and accessible π-electron density can also strengthen the attraction.
Картка 95
Питання
Why do molecular solids usually have low melting points and fail to conduct electricity?
Відповідь
Distinct molecules are held together by relatively weak intermolecular forces, while their valence electrons stay localized in bonds and lone pairs.
Картка 96
Питання
How do particles move in a solid?
Відповідь
They vibrate about fixed positions and do not translate past one another.
Картка 97
Питання
What graph shapes connect V or P with T(K) or n for an ideal gas?
Відповідь
All four are straight lines through the origin: V versus T(K) at fixed n and P; P versus T(K) at fixed n and V; V versus n at fixed P and T; and P versus n at fixed V and T.
Картка 98
Питання
At the same temperature, which gas has the greater average molecular speed: He or Xe?
Відповідь
He. Both have the same average kinetic energy, but KE = ½mv² means the lower-mass particles move faster.
Картка 99
Питання
Why do real gases deviate more at high pressure?
Відповідь
Particles are crowded, so their own volume is no longer negligible compared with the container volume.
Картка 100
Питання
Which relationship describes dilution when solute amount is conserved?
Відповідь
M₁V₁ = M₂V₂.
Картка 101
Питання
Why does an aqueous ionic solution conduct electricity?
Відповідь
Dissolved ions are mobile and carry charge through the solution.
Картка 102
Питання
Which property lets simple distillation separate two liquids?
Відповідь
A sufficient difference in volatility or boiling point, so the vapor is enriched in the more volatile component.
Картка 103
Питання
Why are many ionic compounds soluble in water but poorly soluble in a nonpolar solvent?
Відповідь
Water can form strong ion–dipole attractions that stabilize separated ions; a nonpolar solvent cannot provide comparable attractions.
Картка 104
Питання
Which molecular transition is commonly associated with microwave absorption?
Відповідь
A transition between quantized rotational energy levels.
Картка 105
Питання
What frequency corresponds to a 600. nm photon?
Відповідь
5.00 × 10^14 s^-1. Use ν = c/λ with 600. nm = 6.00 × 10^-7 m.
Картка 106
Питання
What is the absorbance to two significant figures when ε = 2.0 × 10² L mol^-1 cm^-1, b = 1.00 cm, and c = 0.0020 M?
Відповідь
0.40. Use A = εbc.
Картка 107
Питання
What conditions allow hydrogen bonding between two molecules?
Відповідь
One molecule must donate an H covalently bonded to N, O, or F, and the other must provide a lone pair on N, O, or F. A molecule can be a donor, an acceptor, or both.
Картка 108
Питання
Why are covalent-network solids often very hard with high melting points?
Відповідь
A continuous network of strong covalent bonds must be disrupted to deform or melt the solid.
Картка 109
Питання
Why do a substance's solid and liquid phases usually have similar molar volumes?
Відповідь
Their particles remain in close contact in both phases, even though liquid particles can move past one another.
Картка 110
Питання
How is a gas mixture's total pressure related to its component pressures?
Відповідь
Ptotal = ΣPi; each partial pressure is the pressure that component would exert alone in the same volume and temperature.
Картка 111
Питання
What microscopic events create gas pressure?
Відповідь
Gas particles collide with container walls and transfer momentum.
Картка 112
Питання
Why do intermolecular attractions matter more for gases at low temperature?
Відповідь
Particles move more slowly, so attractions can alter their paths and promote condensation.
Картка 113
Питання
What is the final concentration after 50.0 mL of 2.00 M solution is diluted to 200.0 mL?
Відповідь
0.500 M. Use M₂ = M₁V₁/V₂.
Картка 114
Питання
What must a particulate representation of a solution communicate?
Відповідь
The relative concentrations of its components and the particle-level interactions among those components.
Картка 115
Питання
What causes components to separate in chromatography?
Відповідь
They differ in attraction to the stationary phase and the mobile phase, so they travel at different rates.
Картка 116
Питання
Why are many polar molecular solutes soluble in water?
Відповідь
Dipole attractions or hydrogen bonds with water can replace the solute–solute and water–water attractions disrupted during mixing.
Картка 117
Питання
Why does an atom produce discrete spectral lines?
Відповідь
Its electrons can occupy only quantized energy levels, so only photons matching allowed energy differences are absorbed or emitted.
Картка 118
Питання
How does photon energy change when frequency doubles?
Відповідь
It doubles because E = hν.
Картка 119
Питання
Why is a calibration curve useful in spectrophotometry?
Відповідь
It relates measured absorbance to known concentrations, letting an unknown concentration be read by interpolation within the linear range.
Картка 120
Питання
How does an ion–dipole attraction form, and how does it compare with dipole–dipole attraction?
Відповідь
An ion attracts the oppositely charged end of a polar molecule. Ion–dipole attractions tend to be stronger than dipole–dipole attractions.
Картка 121
Питання
Which solid type is usually both conductive and malleable?
Відповідь
A metallic solid, because its delocalized electrons move and its nondirectional bonding tolerates layer shifts.
Картка 122
Питання
How does a crystalline solid differ from an amorphous solid?
Відповідь
A crystalline solid has long-range repeating order; an amorphous solid lacks that long-range periodic arrangement.
Картка 123
Питання
How is a gas component's partial pressure found from mole fraction?
Відповідь
Pi = XiPtotal.
Картка 124
Питання
How does heating a fixed-volume gas affect its pressure in the ideal model?
Відповідь
Pressure rises because faster particles collide with the walls more forcefully and frequently.
Картка 125
Питання
Why can attractions make a real gas's measured pressure lower than the ideal prediction?
Відповідь
Attractions pull approaching particles away from the walls, reducing momentum transfer during wall collisions.
Картка 126
Питання
How many moles of ions result from complete dissolution of 0.20 mol CaCl₂?
Відповідь
0.60 mol ions: 0.20 mol Ca²⁺ plus 0.40 mol Cl⁻.
Картка 127
Питання
How should water orient around Cl⁻ in a particle model?
Відповідь
Its partially positive hydrogen ends point toward Cl⁻.
Картка 128
Питання
Can filtration separate dissolved components of a liquid solution?
Відповідь
No. Dissolved particles pass through the filter with the solvent; filtration only retains an insoluble solid.
Картка 129
Питання
Why do nonpolar molecular solutes often dissolve in nonpolar solvents?
Відповідь
Both rely mainly on compatible London dispersion forces, so mixing can replace the attractions disrupted in the separate substances.
Картка 130
Питання
What does a shorter absorbed wavelength imply about an energy transition?
Відповідь
A larger energy gap because E = hc/λ.
Картка 131
Питання
What is the energy of a photon with frequency 5.0 × 10^14 s^-1?
Відповідь
3.3 × 10^-19 J. Multiply by Planck's constant: E = (6.626 × 10^-34 J·s)(5.0 × 10^14 s^-1).
Картка 132
Питання
How does doubling cuvette path length affect absorbance in the linear Beer–Lambert range?
Відповідь
Absorbance doubles if concentration and molar absorptivity stay constant.
Картка 133
Питання
How can noncovalent interactions affect a large biomolecule?
Відповідь
Attractions between molecules or between different regions of the same molecule help set its shape, which strongly affects its properties and function.
Картка 134
Питання
Why does an ionic solid usually fail to conduct as a solid?
Відповідь
Its ions are fixed in lattice positions. The same substance conducts when molten or dissolved because the ions can then move.
Картка 135
Питання
Why does a gas have no definite shape or volume?
Відповідь
Its widely spaced particles move constantly and experience minimal interparticle attraction, so they spread through the available container.
Картка 136
Питання
What graph shapes show the inverse pressure–volume relationship for a fixed amount of ideal gas at constant temperature?
Відповідь
A plot of P against V is a decreasing curve, while P against 1/V is a straight line through the origin.
Картка 137
Питання
At the same temperature, do different ideal gases have different average kinetic energies?
Відповідь
No. Average translational kinetic energy depends only on absolute temperature.
Картка 138
Питання
Under which conditions is ideal-gas behavior most accurate?
Відповідь
Low pressure and high temperature, where particles are far apart and attractions matter least.
Картка 139
Питання
What particle-level feature distinguishes a solution from a heterogeneous mixture?
Відповідь
A solution—whether solid, liquid, or gas—is uniform throughout; a heterogeneous mixture has regions or phases with different compositions.
Картка 140
Питання
How should water orient around Na⁺ in a particulate model?
Відповідь
Its partially negative oxygen end points toward Na⁺.
Картка 141
Питання
In paper chromatography, why does one solute spot travel farther than another?
Відповідь
It interacts more strongly with the mobile phase or more weakly with the stationary phase. With known phase polarities, that travel difference can reveal relative solute polarity.
Картка 142
Питання
What energy competition helps explain whether an ionic solid dissolves?
Відповідь
The energy needed to separate lattice ions competes with the energy released when ion–solvent attractions form.
Картка 143
Питання
Which molecular motions commonly absorb infrared radiation?
Відповідь
Bond vibrations whose changing dipole can interact with the radiation.
Картка 144
Питання
Why must wavelength be converted to meters in c = λν when c is in m s^-1?
Відповідь
Consistent units are required so meters cancel correctly and frequency comes out in s^-1.
Картка 145
Питання
How can fingerprints on a cuvette affect a visible-light absorbance reading?
Відповідь
They can absorb or scatter extra light, making measured absorbance too high and the inferred concentration too high.
Картка 146
Питання
What causes and controls the strength of dipole–dipole attractions?
Відповідь
Opposite partial charges on neighboring polar molecules attract. Strength increases with larger molecular dipoles and depends on how favorably the dipoles are oriented.
Картка 147
Питання
Why is graphite conductive and soft while diamond is insulating and hard?
Відповідь
Graphite has delocalized electrons within its sheets, so it conducts, and its layers can slide, so it is soft. Diamond has a rigid three-dimensional network of localized covalent bonds, making it hard and insulating.
Картка 148
Питання
Why are gases much more compressible than liquids?
Відповідь
Gas particles have large empty spaces between them; liquid particles are already close together.
Картка 149
Питання
What volume does 0.500 mol CO₂ occupy at 1.00 atm and 300. K if it behaves ideally?
Відповідь
12.3 L. Use V = nRT/P = (0.500 mol)(0.08206 L atm mol^-1 K^-1)(300. K)/(1.00 atm).
Картка 150
Питання
Why does a lighter gas effuse faster than a heavier gas at the same temperature?
Відповідь
Its particles have a higher average speed because equal average kinetic energy is shared by less mass.
Картка 151
Питання
How does finite particle volume affect a real gas at very high pressure?
Відповідь
The free volume available for particle motion is smaller than the container volume assumed by the ideal model.
Картка 152
Питання
How should 250.0 mL of 0.100 M NaCl be prepared from solid NaCl?
Відповідь
Dissolve 0.0250 mol NaCl, or 1.46 g, then dilute to exactly 250.0 mL in a volumetric flask.
Картка 153
Питання
What changes in a particle diagram when a solution is diluted without losing solute?
Відповідь
The solute-particle count stays constant while solvent volume and particle spacing increase.
Картка 154
Питання
Why is fractional distillation better than simple distillation for liquids with close boiling points?
Відповідь
Repeated vaporization–condensation steps enrich the vapor in the more volatile component more effectively.
Картка 155
Питання
Why are oil and water usually immiscible?
Відповідь
Water's strong hydrogen-bond network isn't replaced by equally strong water–oil attractions, so the substances separate into phases.
Картка 156
Питання
Which molecular transition is commonly associated with ultraviolet or visible absorption?
Відповідь
A transition between electronic energy levels.
Картка 157
Питання
Which photon carries more energy, blue light or red light?
Відповідь
Blue light, because it has shorter wavelength and higher frequency.
Картка 158
Питання
Why is absorbance often measured at the wavelength of maximum absorbance in Beer–Lambert analysis?
Відповідь
It gives the largest concentration-sensitive signal, and the flat top near the maximum makes small wavelength-setting errors less influential.
Картка 159
Питання
What creates a dipole–induced-dipole attraction, and what controls its strength?
Відповідь
A permanent dipole distorts a nearby nonpolar particle's electron cloud and creates an attractive temporary dipole. A larger permanent dipole and a more polarizable nonpolar partner make the attraction stronger.
Картка 160
Питання
How do stronger intermolecular forces affect vapor pressure, boiling point, and melting point?
Відповідь
They lower vapor pressure and raise boiling point. Melting point often rises too, but the trend is less direct because melting rearranges rather than fully separates particles.
Картка 161
Питання
How do particles behave in a liquid?
Відповідь
They stay in close contact while moving and colliding continuously. Temperature and interparticle attractions affect their arrangement and motion.
Картка 162
Питання
Why must Celsius temperature be converted to kelvins in gas-law calculations?
Відповідь
Gas-law proportionalities require an absolute temperature scale whose zero corresponds to zero extrapolated thermal motion.
Картка 163
Питання
How does raising temperature change a Maxwell–Boltzmann speed distribution?
Відповідь
The distribution broadens, its peak lowers and shifts right, and a larger fraction of particles have high speed.
Картка 164
Питання
Why does the ideal-gas model treat collisions as elastic?
Відповідь
It assumes total kinetic energy is conserved in particle–particle and particle–wall collisions.
Картка 165
Питання
How many moles of solute are in 75.0 mL of a 0.400 M solution?
Відповідь
0.0300 mol. Multiply 0.400 mol L^-1 by 0.0750 L.
Картка 166
Питання
For equal solution volumes drawn at the same scale, what shows which solution is more concentrated?
Відповідь
The more concentrated diagram contains more solute particles in that equal volume.
Картка 167
Питання
How do differences in intermolecular attractions let distillation separate a liquid solution?
Відповідь
They give the components different vapor pressures, so the vapor is enriched in the more volatile component.
Картка 168
Питання
What comparison helps predict whether two liquids will be miscible?
Відповідь
Liquids with similar types and strengths of intermolecular attractions are more likely to mix uniformly.
Картка 169
Питання
How can an absorption spectrum help identify a substance?
Відповідь
Its allowed energy gaps produce a characteristic pattern of absorbed wavelengths that can be compared with known spectra.
Картка 170
Питання
How does absorbing or emitting a photon change an atom's or molecule's energy?
Відповідь
Absorption raises the species' energy by exactly the photon energy; emission lowers it by the same amount.
Картка 171
Питання
What macroscopic evidence can support that a chemical reaction occurred?
Відповідь
Evidence can include gas formation, precipitate formation, a persistent color change, or an energy change, interpreted with particle-level changes.
Картка 172
Питання
What does a net ionic equation include?
Відповідь
Only the dissolved or reacting species that undergo chemical change; spectator ions are omitted.
Картка 173
Питання
What must a correct particulate reaction diagram conserve?
Відповідь
The number of atoms of every element and the total charge.
Картка 174
Питання
What distinguishes a chemical change from a physical change?
Відповідь
A chemical change rearranges bonds into new substances; a physical change alters state or arrangement without changing chemical identity.
Картка 175
Питання
What does a balanced equation's coefficient ratio provide?
Відповідь
The mole ratio among reacting and produced species.
Картка 176
Питання
What is the equivalence point of a titration?
Відповідь
The point where titrant and analyte have reacted in the stoichiometric ratio given by the balanced equation.
Картка 177
Питання
What defines a precipitation reaction?
Відповідь
Aqueous ions combine to form a sparingly soluble solid.
Картка 178
Питання
What happens in a Brønsted–Lowry acid–base reaction?
Відповідь
A proton transfers from the acid (donor) to the base (acceptor). In aqueous solution, H₂O can play either role.
Картка 179
Питання
What does oxidation mean in a redox reaction?
Відповідь
Loss of electrons and an increase in oxidation number.
Картка 180
Питання
What particle-level change confirms that a process is chemical?
Відповідь
Atoms rearrange into new combinations, producing substances with different compositions.
Картка 181
Питання
Which ions are spectators when AgNO₃(aq) reacts with NaCl(aq)?
Відповідь
Na⁺ and NO₃⁻. The net ionic reaction is Ag⁺(aq) + Cl⁻(aq) → AgCl(s).
Картка 182
Питання
How does a particulate diagram reveal the limiting reactant?
Відповідь
After forming the maximum product allowed by the ratio, none of the limiting reactant remains while excess reactant particles do.
Картка 183
Питання
Is melting ice a chemical or physical change?
Відповідь
A physical change. H₂O molecules remain H₂O while their arrangement and motion change.
Картка 184
Питання
How is the limiting reactant identified from given amounts?
Відповідь
Convert each reactant to the same product amount using the balanced equation; the smaller product amount identifies the limiting reactant.
Картка 185
Питання
How does an endpoint differ from an equivalence point?
Відповідь
The endpoint is an observed signal such as indicator color change; the equivalence point is the exact stoichiometric condition.
Картка 186
Питання
How is complete combustion of a hydrocarbon in excess oxygen classified, and what products form?
Відповідь
It is a redox combustion reaction that forms CO₂ and H₂O.
Картка 187
Питання
What are the conjugate acid and conjugate base in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
Відповідь
NH₄⁺ is the conjugate acid of NH₃, and OH⁻ is the conjugate base of H₂O.
Картка 188
Питання
What does reduction mean in a redox reaction?
Відповідь
Gain of electrons and a decrease in oxidation number.
Картка 189
Питання
Which common changes are physical rather than chemical?
Відповідь
Phase changes and the formation or separation of mixtures are physical when each substance keeps its composition.
Картка 190
Питання
How are strong soluble electrolytes written in a complete ionic equation?
Відповідь
As separated aqueous ions; solids, liquids, gases, and weak electrolytes stay intact.
Картка 191
Питання
A diagram starts with six A particles and four B₂ particles for 2A + B₂ → 2AB; what remains after completion?
Відповідь
One B₂ remains. Six A consume three B₂ and form six AB.
Картка 192
Питання
Why is dissolving NaCl in water normally classified as a physical change?
Відповідь
Na⁺ and Cl⁻ separate and become hydrated, but retain their chemical identities. Removing the water recovers NaCl; the shift from ion–ion to ion–dipole attractions does not by itself form a new substance.
Картка 193
Питання
What mass of AgCl can form from 25.0 mL of 0.200 M AgNO₃ mixed with excess Cl⁻?
Відповідь
0.717 g AgCl. The 1:1 reaction gives 0.00500 mol AgCl; multiply by 143.32 g mol^-1.
Картка 194
Питання
What calculation finds unknown analyte moles at equivalence?
Відповідь
Use titrant moles, n = MV, then apply the balanced-reaction mole ratio.
Картка 195
Питання
Which feature identifies an acid–base, redox, or precipitation reaction?
Відповідь
Acid–base reactions transfer protons, redox reactions change oxidation numbers through electron transfer, and precipitation reactions form a sparingly soluble solid.
Картка 196
Питання
What is the net ionic equation for strong acid–strong base neutralization?
Відповідь
H⁺(aq) + OH⁻(aq) → H₂O(l).
Картка 197
Питання
What is the oxidation number of sulfur in SO₄²⁻?
Відповідь
+6. Four oxygens contribute -8 total, so sulfur must be +6 to give -2 overall.
Картка 198
Питання
Why can gas bubbles alone be ambiguous evidence of reaction?
Відповідь
Bubbles may also come from boiling or dissolved gas escaping, so the context and particle identities must support a chemical change.
Картка 199
Питання
How is melting ice represented as a balanced physical-change equation?
Відповідь
H₂O(s) → H₂O(l). The formula and atom count stay the same because only the physical state changes.
Картка 200
Питання
What does a particle diagram show when no reaction occurs after two aqueous ionic solutions mix?
Відповідь
All ions remain separated and solvated, with no new bonded particles, precipitate, or gas.
Картка 201
Питання
Why is rusting iron a chemical change?
Відповідь
Iron atoms form new iron-oxide substances through electron transfer and new bonding.
Картка 202
Питання
For 2H₂O₂(aq) → 2H₂O(l) + O₂(g), what volume of O₂ forms from 0.100 mol H₂O₂ at 298 K and 1.00 atm?
Відповідь
1.22 L O₂. The mole ratio gives 0.0500 mol O₂, then V = nRT/P.
Картка 203
Питання
A 25.0 mL monoprotic acid sample requires 20.0 mL of 0.150 M NaOH; what is the acid concentration?
Відповідь
0.120 M. At 1:1 equivalence, moles acid = 0.0200 L × 0.150 M, then divide by 0.0250 L.
Картка 204
Питання
Which salts does the minimum solubility rule in this deck treat as soluble?
Відповідь
All salts containing Na⁺, K⁺, NH₄⁺, or NO₃⁻ are treated as soluble in water.
Картка 205
Питання
How are the strengths of a conjugate acid and its conjugate base related?
Відповідь
A stronger acid has a weaker conjugate base, and a stronger base has a weaker conjugate acid.
Картка 206
Питання
How are oxidation and reduction half-reactions combined into one balanced equation?
Відповідь
Multiply them so electrons lost equal electrons gained, add the half-reactions, then cancel electrons and any identical species on both sides.
Картка 207
Питання
How do molecular, complete ionic, and net ionic equations differ?
Відповідь
Molecular equations keep compounds intact, complete ionic equations split strong soluble electrolytes, and net ionic equations remove spectators. All three conserve atoms and charge.
Картка 208
Питання
How should coefficients change particle counts in a reaction diagram?
Відповідь
They set whole-particle ratios while preserving each particle's chemical formula.
Картка 209
Питання
Is separating a mixture by distillation a chemical or physical change?
Відповідь
A physical change. Components change phase and location but keep their chemical identities.
Картка 210
Питання
What equation results from Cu → Cu²⁺ + 2e⁻ and Ag⁺ + e⁻ → Ag?
Відповідь
Cu + 2Ag⁺ → Cu²⁺ + 2Ag. Multiply the silver half-reaction by 2 and cancel 2e⁻; both atom counts and net charge then match.
Картка 211
Питання
How is average reaction rate found from a reactant concentration?
Відповідь
Use the negative concentration change divided by elapsed time, adjusted by its stoichiometric coefficient when comparing species rates.
Картка 212
Питання
What does a rate law express?
Відповідь
It shows how the measured rate depends on reactant concentrations. In rate = k[A]^m[B]^n, m and n are the orders in A and B, and m + n is the overall order.
Картка 213
Питання
A plot of ln[A] versus time is linear; what is the order in A and its integrated rate law?
Відповідь
First order: ln[A]t = ln[A]0 − kt, so the plot's slope is −k.
Картка 214
Питання
What is an elementary reaction?
Відповідь
A single step in a mechanism whose rate law follows directly from its reactant molecularity.
Картка 215
Питання
What two collision conditions are needed for reaction?
Відповідь
Sufficient collision energy and a productive molecular orientation.
Картка 216
Питання
What does activation energy represent on a reaction-energy profile?
Відповідь
The energy difference from the reactants to the transition state. The reaction coordinate tracks the step's structural progress, not elapsed time.
Картка 217
Питання
What must the elementary steps of a valid mechanism do when added?
Відповідь
Cancel intermediates and reproduce the overall balanced reaction.
Картка 218
Питання
How is a proposed mechanism tested against kinetics?
Відповідь
Its derived rate law must agree with the experimentally measured rate law.
Картка 219
Питання
What does a pre-equilibrium approximation assume?
Відповідь
A fast reversible step reaches equilibrium before a later slow step consumes its intermediate.
Картка 220
Питання
What does each peak on a multistep energy profile represent?
Відповідь
A transition state for one elementary step.
Картка 221
Питання
How does a catalyst increase reaction rate?
Відповідь
It provides an alternate mechanism with a lower activation-energy pathway.
Картка 222
Питання
Why does crushing a solid reactant usually increase its reaction rate?
Відповідь
Crushing increases exposed surface area, so more reactant particles can collide with the other reactant each second.
Картка 223
Питання
How is reaction order found from initial-rate data?
Відповідь
Compare trials where one reactant concentration changes while the others stay constant, then match the rate factor to the concentration factor.
Картка 224
Питання
A plot of [A] versus time is linear; what is the order in A and its integrated rate law?
Відповідь
Zero order: [A]t = [A]0 − kt, so the plot's slope is −k.
Картка 225
Питання
What is the rate law for the elementary step 2A + B → products?
Відповідь
rate = k[A]²[B]. This inference is valid because the step is elementary.
450 карток
AP Chemistry Flashcards: Complete 9-Unit Course Review
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Картка 226
Питання
How does raising temperature change a Maxwell–Boltzmann energy distribution and reaction rate?
Відповідь
The distribution shifts and broadens toward higher energies, so a larger fraction of collisions exceeds the activation-energy threshold and can react.
Картка 227
Питання
How is ΔH read from a reaction-energy profile?
Відповідь
ΔH = energy of products − energy of reactants.
Картка 228
Питання
What is a reaction intermediate?
Відповідь
A species formed in one mechanism step and consumed in a later step, so it cancels from the overall equation.
Картка 229
Питання
Why can't overall reaction coefficients usually supply rate-law exponents?
Відповідь
The overall equation hides the mechanism; exponents come from experiment unless the reaction is a stated elementary step.
Картка 230
Питання
How does pre-equilibrium remove an intermediate from a rate law?
Відповідь
Use the fast-step equilibrium relation to express the intermediate concentration in terms of stable reactants.
Картка 231
Питання
What does each valley between peaks represent on a multistep profile?
Відповідь
A reaction intermediate.
Картка 232
Питання
Does a catalyst change ΔH or the equilibrium constant?
Відповідь
No. It changes the pathway and rates, not reactant/product energies or the equilibrium composition.
Картка 233
Питання
For 2A → B, how are disappearance of A and appearance of B related?
Відповідь
Reaction rate = -(1/2)Δ[A]/Δt = Δ[B]/Δt.
Картка 234
Питання
How do the units of k depend on a rate law's overall order?
Відповідь
They must make the rate unit M s^-1: zero order uses M s^-1, first order s^-1, and second order M^-1 s^-1.
Картка 235
Питання
A plot of 1/[A] versus time is linear; what is the order in A and its integrated rate law?
Відповідь
Second order: 1/[A]t = 1/[A]0 + kt, so the plot's slope is +k.
Картка 236
Питання
What is molecularity?
Відповідь
The number of reacting particles in an elementary step, such as unimolecular or bimolecular.
Картка 237
Питання
How does raising temperature affect k in the qualitative Arrhenius model?
Відповідь
k increases, often sharply, because a larger fraction of collisions can reach the transition state. Arrhenius-equation calculations are outside this deck’s scope.
Картка 238
Питання
A reactant falls from 0.80 M to 0.50 M in 30. s; what is its average disappearance rate to two significant figures?
Відповідь
0.010 M s^-1. Use -(0.50 − 0.80) M ÷ 30. s.
Картка 239
Питання
How does a catalyst differ from an intermediate in a mechanism?
Відповідь
A catalyst is consumed early and regenerated later; an intermediate is formed early and consumed later.
Картка 240
Питання
For 2NO₂ → NO₃ + NO (slow), followed by NO₃ + CO → NO₂ + CO₂ (fast), what rate law is predicted?
Відповідь
rate = k[NO₂]². The first step is elementary and rate-limiting, so its molecularity sets the observed rate law.
Картка 241
Питання
On a multistep reaction-energy profile, which feature often identifies the rate-determining step?
Відповідь
The step with the largest activation barrier measured from its preceding valley to its peak.
Картка 242
Питання
If changing [B] leaves rate unchanged, what is the order in B?
Відповідь
Zero order, so [B]^0 = 1 in the measured rate law.
Картка 243
Питання
What mechanism changes can binding, acid–base, or surface catalysis introduce?
Відповідь
They can orient reactants, lower activation barriers, or create new bound, protonated, or deprotonated intermediates and elementary steps; the catalyst is regenerated.
Картка 244
Питання
What is special about a first-order reaction's half-life?
Відповідь
It is constant and independent of starting concentration: t1/2 = ln 2/k. Radioactive decay is a common first-order example.
Картка 245
Питання
Why is a termolecular elementary collision uncommon?
Відповідь
Three particles must collide simultaneously with suitable energy and orientation, which is much less probable than one- or two-particle events.
Картка 246
Питання
On a reaction-energy profile, how are reverse activation energy, forward activation energy, and ΔH related?
Відповідь
Ea,reverse = Ea,forward − ΔH. The reverse barrier is measured from products to the same transition state.
Картка 247
Питання
Why can correct orientation matter even above the activation energy?
Відповідь
The colliding reactive sites must align so old bonds can break and new bonds can form along the reaction pathway.
Картка 248
Питання
How does detecting a proposed reaction intermediate affect a mechanism claim?
Відповідь
It supports a mechanism that contains that intermediate, but it doesn't prove that mechanism is unique.
Картка 249
Питання
For 2NO ⇌ N₂O₂ (fast equilibrium), followed by N₂O₂ + O₂ → 2NO₂ (slow), what observed rate law results?
Відповідь
rate = kobs[NO]²[O₂]. Start with rate = k₂[N₂O₂][O₂], use [N₂O₂] = K[NO]² from the fast equilibrium, then substitute.
Картка 250
Питання
What does the highest point of a one-step energy profile represent?
Відповідь
The transition state, an unstable arrangement at the top of the activation barrier.
Картка 251
Питання
What sign does q have for an endothermic system?
Відповідь
Positive, because the system absorbs heat from the surroundings.
Картка 252
Питання
How does an exothermic reaction appear on an enthalpy diagram?
Відповідь
Products lie below reactants, so ΔH is negative.
Картка 253
Питання
What condition defines thermal equilibrium?
Відповідь
Objects in contact have the same temperature, so there is no net heat transfer.
Картка 254
Питання
What equations relate heat capacity and temperature change to heat transfer?
Відповідь
Use q = mcΔT with specific heat capacity, or q = nCₘΔT with molar heat capacity.
Картка 255
Питання
Why is temperature constant during a phase-change plateau?
Відповідь
Added or removed energy changes interparticle potential energy instead of average kinetic energy.
Картка 256
Питання
What does ΔHrxn describe?
Відповідь
The heat absorbed or released at constant pressure for the reaction exactly as written under the stated conditions.
Картка 257
Питання
How is reaction enthalpy estimated from average bond enthalpies?
Відповідь
ΔHrxn ≈ Σ(bonds broken) − Σ(bonds formed).
Картка 258
Питання
What is the standard enthalpy of formation of an element in its standard state?
Відповідь
Zero by definition.
Картка 259
Питання
In a Hess’s law calculation, how should a step change when the target needs twice its reverse?
Відповідь
Reverse the equation, double every coefficient, and multiply its ΔH by -2.
Картка 260
Питання
How can energy cross a system boundary during a process?
Відповідь
As heat or work. Heat transferred to or work done on the system increases its energy; heat transferred from or work done by the system decreases it.
Картка 261
Питання
How does an endothermic reaction appear on an enthalpy diagram?
Відповідь
Products lie above reactants, so ΔH is positive.
Картка 262
Питання
How are heat gained by a system and heat lost by its surroundings related in an isolated setup?
Відповідь
qsystem = -qsurroundings.
Картка 263
Питання
In coffee-cup calorimetry, how is reaction heat related to solution heat?
Відповідь
qrxn = -qsolution when calorimeter heat is negligible and pressure is constant.
Картка 264
Питання
What heat is required to melt n moles at the melting point?
Відповідь
q = nΔHfus.
Картка 265
Питання
How does reversing a reaction change ΔH?
Відповідь
It reverses the sign of ΔH.
Картка 266
Питання
Why is breaking a bond endothermic?
Відповідь
Energy must be supplied to separate atoms against their bonding attraction.
Картка 267
Питання
How is ΔH°rxn calculated from standard enthalpies of formation?
Відповідь
ΣνΔHf°(products) − ΣνΔHf°(reactants).
Картка 268
Питання
How does multiplying an equation by 3 affect its ΔH?
Відповідь
Multiply ΔH by 3 because enthalpy change scales with reaction amount.
Картка 269
Питання
Why can an exothermic dissolution warm the solution?
Відповідь
The solution warms because forming solute–solvent attractions releases more energy than is absorbed in separating the original particles. The net potential-energy decrease raises particle kinetic energy and temperature.
Картка 270
Питання
Does an energy diagram's activation barrier determine ΔH?
Відповідь
No. ΔH depends on reactant and product energy levels, while the barrier controls kinetics.
Картка 271
Питання
Why does heat flow from a warmer object to a cooler object?
Відповідь
Energy transfers through collisions until their average kinetic energies, and therefore temperatures, equalize.
Картка 272
Питання
How much heat warms 100.0 g of water by 5.0°C?
Відповідь
2.1 kJ. Use q = (100.0 g)(4.184 J g^-1 °C^-1)(5.0°C).
Картка 273
Питання
How are the molar enthalpies of a phase change and its reverse related?
Відповідь
They have equal magnitudes and opposite signs, such as ΔHcond = -ΔHvap and ΔHfreeze = -ΔHfus.
Картка 274
Питання
How does doubling every coefficient in a thermochemical equation affect ΔH?
Відповідь
It doubles ΔH.
Картка 275
Питання
Why is forming a bond exothermic?
Відповідь
Atoms move to a lower-potential-energy bonded arrangement and release energy.
Картка 276
Питання
What formation equation defines ΔHf° for CO₂(g)?
Відповідь
C(s, graphite) + O₂(g) → CO₂(g), forming exactly one mole from elements in standard states.
Картка 277
Питання
What should happen to intermediate species when equations in a Hess’s law calculation are added?
Відповідь
They cancel, leaving the target overall reaction.
Картка 278
Питання
If the surroundings warm during a process, what is the likely sign of qsystem?
Відповідь
Negative; the system likely released heat to the surroundings.
Картка 279
Питання
For a profile with reactants at 40 kJ and products at 10 kJ, what is ΔH?
Відповідь
-30 kJ for the reaction as drawn.
Картка 280
Питання
Assuming no phase change, what determines the final temperature when two substances exchange heat in an insulated container?
Відповідь
Energy conservation: q_warm + q_cool = 0. Use each substance's mass, heat capacity, and initial temperature to solve for the common final temperature.
Картка 281
Питання
How would heat loss to the room affect an exothermic calorimetry result?
Відповідь
The observed temperature rise is too small, so the calculated magnitude of released heat is too low.
Картка 282
Питання
What heat expression covers warming a liquid without a phase change?
Відповідь
q = mcΔT, not nΔHphase.
Картка 283
Питання
If forming 1 mol of product has ΔH = -50 kJ mol^-1, what is q when 2 mol forms?
Відповідь
-100 kJ. Use q = nΔH = (2 mol)(-50 kJ mol^-1).
Картка 284
Питання
Breaking reactant bonds requires 500 kJ, and forming product bonds releases 650 kJ; what is the estimated ΔH?
Відповідь
-150 kJ, from 500 − 650.
Картка 285
Питання
For CO(g) + ½O₂(g) → CO₂(g), what is ΔH°rxn if ΔHf°[CO] = -110.5 and ΔHf°[CO₂] = -393.5 kJ mol^-1?
Відповідь
-283.0 kJ. Use -393.5 - [-110.5 + ½(0)], since ΔHf°[O₂(g)] = 0.
Картка 286
Питання
In a Hess’s law calculation, two valid steps have ΔH values +25 kJ and -60 kJ; what is the combined ΔH?
Відповідь
-35 kJ, provided the equations add to the target reaction.
Картка 287
Питання
Why is “bonds breaking releases energy” incorrect?
Відповідь
Bond breaking absorbs energy; the overall reaction releases energy only when forming new bonds releases more than breaking old bonds requires.
Картка 288
Питання
How would melting appear on an energy diagram?
Відповідь
The liquid lies above the solid, so ΔHfus is positive; the diagram represents a physical, endothermic change.
Картка 289
Питання
Can two objects at the same temperature exchange energy microscopically?
Відповідь
Yes, but their energy transfers balance, so there is no net heat flow.
Картка 290
Питання
Why must the calorimeter's heat capacity be included when it isn't negligible?
Відповідь
The apparatus can absorb or release heat, so include q_cal = C_calΔT in the energy balance: q_process + q_solution + q_cal = 0.
Картка 291
Питання
What makes chemical equilibrium dynamic?
Відповідь
Forward and reverse reactions continue at equal rates even though macroscopic concentrations stay constant.
Картка 292
Питання
For aA + bB ⇌ cC, what is the concentration-form expression for Q?
Відповідь
Q = [C]^c / ([A]^a[B]^b), using current rather than necessarily equilibrium concentrations.
Картка 293
Питання
What does K much greater than 1 indicate?
Відповідь
Products predominate at equilibrium, though K says nothing about reaction speed.
Картка 294
Питання
How does reversing a reaction change its equilibrium constant?
Відповідь
K becomes 1/K.
Картка 295
Питання
Can a reversible system reach equilibrium when it starts with only products?
Відповідь
Yes, if the reverse reaction is possible. The equilibrium composition depends on temperature, initial amounts, and volume or pressure.
Картка 296
Питання
How do Q and K predict reaction direction?
Відповідь
Q < K shifts forward, Q > K shifts reverse, and Q = K means equilibrium.
Картка 297
Питання
Which species are omitted from a heterogeneous equilibrium expression?
Відповідь
Pure solids and pure liquids because their activities are effectively constant.
Картка 298
Питання
How does increasing a dissolved reactant's concentration or a gaseous reactant's partial pressure affect equilibrium at constant temperature when other Q terms are initially unchanged?
Відповідь
It lowers Q relative to K, so the system shifts toward products until Q = K again. Changing the amount of a pure solid or liquid omitted from Q does not cause this shift while that pure phase remains present.
Картка 299
Питання
What does a flat concentration-time graph mean at equilibrium?
Відповідь
Each concentration is constant, not necessarily equal to the others.
Картка 300
Питання
For A ⇌ B in one fixed volume, a particulate model shows 16 A and 0 B initially, then 4 A and 12 B at equilibrium. What changed, what predominates, and what is Kc?
Відповідь
The net change was forward: 12 A particles became 12 B particles. B predominates at equilibrium, and Kc = [B]/[A] = 12/4 = 3.0 because both counts come from the same fixed volume.
Картка 301
Питання
What can Ksp tell you about a salt's solubility, and when can two Ksp values be compared directly?
Відповідь
Ksp > 1 indicates a soluble salt. For salts with the same dissolution stoichiometry, a larger Ksp generally means greater molar solubility; across different stoichiometries, calculate molar solubility before comparing.
Картка 302
Питання
What is the common-ion effect on solubility?
Відповідь
Adding an ion already in the dissolution equilibrium usually decreases the solid's molar solubility.
Картка 303
Питання
How does uniform dilution shift an aqueous equilibrium based on the stoichiometric powers in Q?
Відповідь
It shifts toward the side with the larger sum of stoichiometric coefficients for dissolved species included in Q. If the sums are equal, dilution causes no shift by this effect; pure solids and liquids remain omitted.
Картка 304
Питання
What happens if a reversible reaction starts with reactants only?
Відповідь
The forward rate is initially largest; products form, the reverse rate grows, and the rates eventually become equal.
Картка 305
Питання
What is the purpose of an ICE table?
Відповідь
To organize initial, change, and equilibrium concentrations using reaction stoichiometry.
Картка 306
Питання
Can a reaction with a very large K be slow?
Відповідь
Yes. K describes thermodynamic equilibrium position, while rate depends on kinetics and activation energy.
Картка 307
Питання
What happens to Q immediately after product concentration increases?
Відповідь
Q increases; if it rises above K, the reaction shifts toward reactants.
Картка 308
Питання
How does multiplying every reaction coefficient by 2 affect K?
Відповідь
The new equilibrium constant is K².
Картка 309
Питання
For A ⇌ B, Kc = 4.0 and initially [A] = 1.0 M and [B] = 0, what are the equilibrium concentrations?
Відповідь
[A] = 0.20 M and [B] = 0.80 M. Let x form: Kc = x/(1.0 − x) = 4.0, so x = 0.80 M.
Картка 310
Питання
What macroscopic properties stay constant at equilibrium?
Відповідь
Properties such as concentration, color, and pressure remain constant when external conditions are fixed.
Картка 311
Питання
How does decreasing volume shift a gaseous equilibrium?
Відповідь
Toward the side with fewer moles of gas, if the two sides have different gaseous mole counts.
Картка 312
Питання
For N₂ + 3H₂ ⇌ 2NH₃, what is Kc?
Відповідь
Kc = [NH₃]² / ([N₂][H₂]³).
Картка 313
Питання
For CaF₂(s) ⇌ Ca²⁺ + 2F⁻, how is Ksp written in terms of molar solubility s in pure water?
Відповідь
Ksp = s(2s)² = 4s³ because [Ca²⁺] = s and [F⁻] = 2s.
Картка 314
Питання
What does K much less than 1 indicate?
Відповідь
Reactants predominate at equilibrium.
Картка 315
Питання
How does decreasing a dissolved product's concentration or a gaseous product's partial pressure affect equilibrium when other Q terms are initially unchanged?
Відповідь
It lowers Q and drives a net forward reaction until equilibrium returns. Changing the amount of a pure solid or liquid omitted from Q does not cause this shift while that phase remains.
Картка 316
Питання
Does equilibrium mean the reaction has stopped?
Відповідь
No. Both directions continue, but equal rates produce no net macroscopic change.
Картка 317
Питання
Why does adding NaF reduce CaF₂ solubility?
Відповідь
The added F⁻ raises Qsp, shifting the dissolution equilibrium toward solid CaF₂.
Картка 318
Питання
For N₂ + 3H₂ ⇌ 2NH₃, what is Kp when P_N₂ = 0.50 atm, P_H₂ = 1.50 atm, and P_NH₃ = 0.25 atm?
Відповідь
0.037. Use Kp = (P_NH₃)²/[(P_N₂)(P_H₂)³] = (0.25)²/[(0.50)(1.50)³]. Use equilibrium partial pressures directly; Kc↔Kp conversion isn't assessed.
Картка 319
Питання
What happens to Q when a gaseous equilibrium mixture is compressed at constant temperature if products have fewer gas moles?
Відповідь
Q falls relative to K, so the reaction shifts toward products.
Картка 320
Питання
How do K and Q transform when a reaction is reversed, its coefficients are multiplied, or reactions are added?
Відповідь
They follow the same algebra: reversing takes the reciprocal, multiplying every coefficient by c raises the value to the power c, and adding reactions multiplies their K or Q values.
Картка 321
Питання
When is the small-x approximation acceptable?
Відповідь
When x is small relative to the initial concentration and the final result confirms the neglected change is suitably small.
Картка 322
Питання
What graph feature shows a disturbance followed by re-equilibration?
Відповідь
A sudden or gradual concentration change followed by new constant plateaus while rates return to equality.
Картка 323
Питання
If Q = 0.20 and K = 5.0, which direction is favored next?
Відповідь
Forward, because Q < K.
Картка 324
Питання
At equilibrium, are reactant and product concentrations equal?
Відповідь
Not necessarily. They are constant, while forward and reverse rates are equal.
Картка 325
Питання
CaF₂ has Ksp = 3.2 × 10^-11 in pure water; what is its molar solubility?
Відповідь
2.0 × 10^-4 M. If the molar solubility is s, then [Ca²⁺] = s, [F⁻] = 2s, and Ksp = 4s³.
Картка 326
Питання
For N₂ + 3H₂ ⇌ 2NH₃, how is Qp written?
Відповідь
Qp = (P_NH₃)²/[(P_N₂)(P_H₂)³], using the current partial pressures rather than necessarily equilibrium values.
Картка 327
Питання
How does heating shift an endothermic forward reaction?
Відповідь
Toward products, and K increases because temperature changes the equilibrium constant.
Картка 328
Питання
Why do both forward and reverse rates change as equilibrium is approached?
Відповідь
As reactant and product concentrations change, the collision frequencies for the two directions change until their rates match.
Картка 329
Питання
CaF₂ has Ksp = 3.2 × 10^-11. What is its molar solubility in 0.10 M NaF?
Відповідь
About 3.2 × 10^-9 M. With [F⁻] ≈ 0.10 M, Ksp = [Ca²⁺][F⁻]² gives s = (3.2 × 10^-11)/(0.10)². The common ion lowers solubility but does not change Ksp at constant temperature.
Картка 330
Питання
What concentration data must be used to calculate Kc?
Відповідь
Equilibrium concentrations, each raised to its stoichiometric coefficient and excluding pure solids and liquids.
Картка 331
Питання
What is a Brønsted–Lowry acid?
Відповідь
A proton donor.
Картка 332
Питання
How is pH defined?
Відповідь
pH = -log[H₃O⁺].
Картка 333
Питання
What is Ka for HA + H₂O ⇌ H₃O⁺ + A⁻?
Відповідь
Ka = [H₃O⁺][A⁻]/[HA].
Картка 334
Питання
How does stabilizing a base affect its basicity and the strength of its conjugate acid?
Відповідь
It makes the base weaker and its conjugate acid stronger. A more stable base is less willing to accept H⁺.
Картка 335
Питання
What is a Brønsted–Lowry base?
Відповідь
A proton acceptor.
Картка 336
Питання
At 25°C, what are Kw and the relationship between pH and pOH?
Відповідь
Kw = [H₃O⁺][OH⁻] = 1.0 × 10^-14. Taking negative logarithms gives pH + pOH = 14.00.
Картка 337
Питання
What is Kb for B + H₂O ⇌ BH⁺ + OH⁻?
Відповідь
Kb = [BH⁺][OH⁻]/[B].
Картка 338
Питання
Why can lowering pH increase the solubility of a salt containing a basic anion?
Відповідь
H₃O⁺ consumes the anion, pulling the dissolution equilibrium toward more dissolved ions.
Картка 339
Питання
What are conjugate acid–base pairs?
Відповідь
Species that differ by exactly one proton.
Картка 340
Питання
What is the pH of 1.0 × 10^-3 M HCl?
Відповідь
3.00, assuming complete dissociation and negligible water contribution.
Картка 341
Питання
How are pKa and pKb defined?
Відповідь
pKa = -log Ka, and pKb = -log Kb.
Картка 342
Питання
Why does acid strength increase across a row of comparable hydrides?
Відповідь
Increasing electronegativity stabilizes the conjugate base and polarizes the H–A bond.
Картка 343
Питання
What is an amphiprotic species?
Відповідь
A species that can donate or accept a proton, such as HCO₃⁻.
Картка 344
Питання
What amounts remain after a limited amount of strong base partially neutralizes weak acid HA?
Відповідь
Subtract the reacted moles from HA and form the same number of moles of A⁻. The result gives the remaining HA and formed A⁻ amounts before any equilibrium or buffer-pH calculation.
Картка 345
Питання
How are Ka, Kb, pKa, and pKb related for a conjugate pair at 25°C?
Відповідь
KaKb = Kw = 1.0 × 10^-14, and pKa + pKb = pKw = 14.00.
Картка 346
Питання
When does pH have little effect on a salt's solubility?
Відповідь
When neither dissolved ion reacts appreciably with H₃O⁺ or OH⁻.
Картка 347
Питання
How does H₂O act in HCl + H₂O → H₃O⁺ + Cl⁻ and in NH₃ + H₂O ⇌ NH₄⁺ + OH⁻?
Відповідь
It acts as a base in the first reaction by accepting H⁺, and as an acid in the second by donating H⁺.
Картка 348
Питання
After mixing weak base B with strong acid, what controls the final solution in the three stoichiometric regimes?
Відповідь
Excess B leaves a B/BH⁺ buffer; equimolar amounts leave BH⁺, so the solution is acidic; excess strong acid sets the pH from the remaining H₃O⁺.
Картка 349
Питання
What two components make a typical weak-acid buffer?
Відповідь
A weak acid and a significant amount of its conjugate base.
Картка 350
Питання
What do the successive half-equivalence pH values approximate in a diprotic weak-acid titration?
Відповідь
The first approximates pKa₁ and the second approximates pKa₂ because each conjugate pair has equal concentrations at its half-equivalence point.
Картка 351
Питання
Which acid is stronger, one with pKa 2 or pKa 5?
Відповідь
The acid with pKa 2; lower pKa means larger Ka.
Картка 352
Питання
What is the Henderson–Hasselbalch equation?
Відповідь
pH = pKa + log([A⁻]/[HA]).
Картка 353
Питання
Why are larger binary hydrides down a group often stronger acids?
Відповідь
The H–A bond becomes weaker as the central atom grows, so proton release is easier.
Картка 354
Питання
What mainly determines buffer capacity?
Відповідь
The concentrations of both members of the conjugate acid–base pair. Increasing both concentrations at a fixed ratio increases capacity without changing pH; capacity is best balanced for added acid and base when their concentrations are similar.
Картка 355
Питання
Why does acid increase CaCO₃ solubility?
Відповідь
H₃O⁺ converts CO₃²⁻ to HCO₃⁻ or carbonic acid species, reducing free carbonate and driving more CaCO₃ to dissolve.
Картка 356
Питання
What does pH < pKa imply for a weak-acid pair?
Відповідь
The protonated form HA predominates over A⁻.
Картка 357
Питання
What happens when stoichiometrically equal amounts of a monoprotic weak acid and strong base are mixed?
Відповідь
The weak acid is consumed to its conjugate base; at equivalence, the solution isn't a buffer containing both forms.
Картка 358
Питання
What is [H₃O⁺] when pH = 4.50?
Відповідь
3.2 × 10^-5 M, from [H₃O⁺] = 10^-pH.
Картка 359
Питання
What is the pH of 0.010 M Ba(OH)₂ at 25°C?
Відповідь
About 12.30. Complete dissociation gives [OH⁻] = 0.020 M, so pOH = 1.70. At 25°C, pH + pOH = 14.00, so pH = 12.30.
Картка 360
Питання
How does a buffer respond to a small amount of added strong acid?
Відповідь
Its conjugate base consumes H⁺, converting to the weak acid and limiting the pH change.
Картка 361
Питання
Why is the equivalence-point solution basic in a monoprotic weak-acid–strong-base titration?
Відповідь
The conjugate base produced at equivalence reacts with water to form OH⁻, so the pH is above neutral—above 7.00 at 25°C.
Картка 362
Питання
How is percent ionization calculated for a weak acid or weak base?
Відповідь
For HA, use ([H₃O⁺]equilibrium ÷ [HA]initial) × 100%. For B, use ([BH⁺]equilibrium ÷ [B]initial) × 100%, under the usual monoprotic setup.
Картка 363
Питання
When is Henderson–Hasselbalch useful for an initial buffer-pH calculation?
Відповідь
Use it when both members of a conjugate acid–base pair are present in meaningful amounts, including after in-scope stoichiometry creates a buffer. Calculating the pH change after acid or base is added to an existing buffer is outside this deck’s scope.
Картка 364
Питання
Why does adding oxygen atoms usually strengthen oxyacids with the same central atom?
Відповідь
Extra oxygens withdraw electron density and delocalize negative charge in the conjugate base.
Картка 365
Питання
A prepared buffer is accidentally diluted to twice its intended volume; what happens to its pH and capacity?
Відповідь
Its pH stays nearly the same, and its capacity per liter is halved because both component concentrations halve. The total neutralizing moles in the sample remain unchanged.
Картка 366
Питання
How does adding OH⁻ affect Mg(OH)₂ solubility?
Відповідь
It decreases solubility through the common-ion effect, shifting Mg(OH)₂(s) ⇌ Mg²⁺ + 2OH⁻ toward the solid.
Картка 367
Питання
A buffer has equal [A⁻] and [HA]; what is its pH?
Відповідь
pH = pKa because log(1) = 0.
Картка 368
Питання
How should a weak acid–strong base mixture be solved before equivalence?
Відповідь
First use mole stoichiometry; if both HA and A⁻ remain, use the resulting buffer relation.
Картка 369
Питання
Why can pure neutral water have a pH other than 7.00?
Відповідь
Kw changes with temperature. Neutrality means [H₃O⁺] = [OH⁻], while pH = 7.00 only when Kw = 1.0 × 10^-14 at 25°C.
Картка 370
Питання
25.0 mL of 0.200 M HCl is diluted to 100.0 mL; what is the pH?
Відповідь
1.301. Dilution gives [H₃O⁺] = (0.200 M)(25.0 mL)/(100.0 mL) = 0.0500 M, so pH = -log(0.0500).
Картка 371
Питання
How does a buffer respond to a small amount of added strong base?
Відповідь
The weak acid consumes OH⁻, forming conjugate base and water.
Картка 372
Питання
How do you find the final pH after mixing a strong acid and strong base at 25°C?
Відповідь
Use H₃O⁺ + OH⁻ → 2H₂O and compare their moles. Divide excess H₃O⁺ or OH⁻ by the total volume, then calculate pH or pOH from that excess concentration. Equal moles give pH 7.00 at 25°C.
Картка 373
Питання
What distinguishes acid strength from acid concentration?
Відповідь
Strength is the equilibrium tendency to donate H⁺, reflected by Ka or pKa; concentration is the amount of acid per solution volume.
Картка 374
Питання
If [A⁻]/[HA] = 10, how does pH compare with pKa?
Відповідь
pH = pKa + 1 because log 10 = 1.
Картка 375
Питання
Which conjugate base is more stable, one with localized or resonance-delocalized charge?
Відповідь
The resonance-delocalized conjugate base, which generally corresponds to the stronger acid.
Картка 376
Питання
Which 1.0 L buffer has greater capacity: 1.0 mol each of HA/A⁻ or 0.10 mol each at the same ratio?
Відповідь
The 1.0 mol pair; both have the same initial pH, but the larger amounts neutralize more added acid or base.
Картка 377
Питання
For BHX(s) ⇌ BH⁺ + X⁻, why can raising pH increase the salt's solubility?
Відповідь
OH⁻ consumes BH⁺ to form B and H₂O, so dissolution shifts right to replace BH⁺. This is a qualitative prediction, not a pH-dependent solubility calculation.
Картка 378
Питання
What does pH > pKa imply for a weak-acid pair?
Відповідь
The deprotonated form A⁻ predominates over HA.
Картка 379
Питання
For HA + B ⇌ A⁻ + BH⁺, which side is favored when pKa(HA) = 4 and pKa(BH⁺) = 9?
Відповідь
Products are favored. Proton transfer moves toward the weaker acid–base pair, and K ≈ 10^(9 − 4) = 10^5.
Картка 380
Питання
What is the pOH when [OH⁻] = 2.5 × 10^-4 M?
Відповідь
3.60, from -log(2.5 × 10^-4).
Картка 381
Питання
What is the pH of 0.100 M HA when Ka = 1.0 × 10^-5?
Відповідь
About 3.00. The ICE setup gives Ka = x²/(0.100 − x); x ≈ 1.0 × 10^-3 M, and the 1.0% change validates the approximation.
Картка 382
Питання
Why does a buffer fail after too much strong acid is added?
Відповідь
Its conjugate base is depleted, so added H⁺ is no longer consumed effectively.
Картка 383
Питання
What do two clear equivalence regions on an acid titration curve suggest?
Відповідь
At least two distinguishable titratable protons; on a clean ideal curve with exactly two equivalence regions, this is consistent with a diprotic acid.
Картка 384
Питання
A buffer has pKa 4.8 and [A⁻]/[HA] = 0.10; what is pH?
Відповідь
3.8, from 4.8 + log(0.10).
Картка 385
Питання
Why is HCl stronger than HF in water despite F being more electronegative?
Відповідь
The H–F bond is much stronger; bond strength dominates this down-group binary-acid comparison.
Картка 386
Питання
Why does percent ionization increase when a weak acid is diluted?
Відповідь
Dilution shifts ionization toward more particles, so a larger fraction ionizes even though [H₃O⁺] decreases.
Картка 387
Питання
A buffer contains more HA than A⁻. Which addition can it neutralize in greater amount: strong acid or strong base?
Відповідь
Strong base. The larger HA reserve consumes more added OH⁻; a buffer with more A⁻ than HA instead has greater capacity for added strong acid.
Картка 388
Питання
Why can removing a basic anion increase a salt's molar solubility without changing Ksp?
Відповідь
The equilibrium shifts to replace the consumed ion; Ksp remains fixed at the same temperature.
Картка 389
Питання
Why can an acid–base indicator change color as pH changes?
Відповідь
Its protonated and deprotonated forms have different colors or other observable properties, and their relative amounts change with pH.
Картка 390
Питання
What buffer results from mixing 1.0 mol HA with 0.40 mol OH⁻?
Відповідь
0.60 mol HA and 0.40 mol A⁻ remain, forming a buffer before any equilibrium calculation.
Картка 391
Питання
What is the pH of 0.200 M weak base B when Kb = 2.0 × 10^-5 at 25°C?
Відповідь
About 11.30. The ICE setup gives Kb = x²/(0.200 − x); x ≈ 2.0 × 10^-3 M OH⁻, and the 1.0% change validates the approximation.
Картка 392
Питання
Why does a weak acid alone not make an effective buffer?
Відповідь
It lacks a substantial conjugate-base reserve to consume added strong acid.
Картка 393
Питання
What controls pH after excess strong base passes equivalence?
Відповідь
The concentration of excess OH⁻ after accounting for reaction stoichiometry and total volume.
Картка 394
Питання
How should an indicator be chosen for a titration?
Відповідь
Its color-change range should fall within the steep pH change near the equivalence point.
Картка 395
Питання
How can a measured pH and known pKa give a conjugate-base/acid ratio?
Відповідь
Rearrange Henderson–Hasselbalch: [A⁻]/[HA] = 10^(pH − pKa).
Картка 396
Питання
Can a weak base and its conjugate acid form a buffer?
Відповідь
Yes, when both are present in significant amounts.
Картка 397
Питання
For equal-volume buffers with the same conjugate-base/acid ratio, how does adding the same amount of strong acid affect a more concentrated versus less concentrated buffer?
Відповідь
The concentrated buffer changes pH less because it has greater capacity.
Картка 398
Питання
How does equivalence-point pH compare for strong acid–strong base, weak acid–strong base, and weak base–strong acid titrations at 25°C?
Відповідь
Strong acid–strong base: pH 7.00. Weak acid–strong base: above 7.00 because the conjugate base reacts with water. Weak base–strong acid: below 7.00 because the conjugate acid reacts with water.
Картка 399
Питання
Why should mole ratios replace concentration ratios after mixing buffer solutions?
Відповідь
Both components share the same final volume, so that volume cancels in [A⁻]/[HA].
Картка 400
Питання
How does adding a little strong acid change a buffer's conjugate-base and conjugate-acid amounts?
Відповідь
The conjugate base decreases and its conjugate acid increases by the amount of strong acid consumed.
Картка 401
Питання
What does entropy measure qualitatively?
Відповідь
The dispersal of matter and energy among available microstates.
Картка 402
Питання
How is standard reaction entropy calculated?
Відповідь
ΔS°rxn = ΣνS°(products) − ΣνS°(reactants).
Картка 403
Питання
What equation gives ΔG° from ΔH° and ΔS°, and what standard states do the degree symbols assume?
Відповідь
ΔG° = ΔH° − TΔS°. The standard states are pure substances, 1.0 M solutions, and gases at 1 atm or 1 bar; T is in kelvins and energy units must match.
Картка 404
Питання
Does thermodynamic favorability guarantee a fast reaction?
Відповідь
No. A favorable reaction can be slow when its activation barrier is large.
Картка 405
Питання
What is ΔG at equilibrium?
Відповідь
Zero under the current conditions because there is no net driving force.
Картка 406
Питання
Why can an endothermic dissolution still be thermodynamically favorable?
Відповідь
A sufficiently positive entropy change can make TΔS exceed positive ΔH, giving negative ΔG.
Картка 407
Питання
How can an unfavorable reaction be driven by a favorable one?
Відповідь
Couple them so their equations and ΔG values add to a negative overall ΔG.
Картка 408
Питання
Where does oxidation occur in every electrochemical cell?
Відповідь
At the anode.
Картка 409
Питання
How are standard cell potential and standard free energy related?
Відповідь
ΔG° = -nFE°cell.
Картка 410
Питання
What equation gives cell potential under nonstandard conditions?
Відповідь
E = E° − (RT/nF) ln Q. When Q = 1, ln Q = 0, so E = E°.
Картка 411
Питання
How is electrical charge related to current and time?
Відповідь
q = It.
Картка 412
Питання
Which phase has greater molar entropy, liquid water or ice at the same temperature?
Відповідь
Liquid water because its molecules have more accessible arrangements and motion.
Картка 413
Питання
Do elements in their standard states have zero standard molar entropy?
Відповідь
No. Their ΔHf° is zero, but their absolute S° values are positive above 0 K.
Картка 414
Питання
How do the four ΔH° and ΔS° sign combinations determine thermodynamic favorability across temperature?
Відповідь
ΔH° < 0 and ΔS° > 0 is favorable at every temperature; ΔH° > 0 and ΔS° < 0 is thermodynamically unfavored at every temperature. If both are positive, favorability requires high temperature; if both are negative, it requires low temperature.
Картка 415
Питання
What does it indicate when a thermodynamically favored process does not occur at a measurable rate?
Відповідь
It is under kinetic control, commonly because of a high activation energy; no measurable reaction does not mean the system is at equilibrium.
Картка 416
Питання
How are ΔG° and K related?
Відповідь
ΔG° = -RT ln K.
Картка 417
Питання
What two contributions compete in dissolving an ionic solid?
Відповідь
Enthalpy changes from separating and solvating particles, and entropy changes from their new dispersal and solvent organization.
Картка 418
Питання
What must cancel when coupled reactions are added?
Відповідь
Shared intermediates, leaving the desired net reaction.
Картка 419
Питання
Where does reduction occur in every electrochemical cell?
Відповідь
At the cathode.
Картка 420
Питання
What sign of E°cell indicates a favorable standard galvanic reaction?
Відповідь
Positive E°cell, corresponding to negative ΔG°.
Картка 421
Питання
If Q increases for a galvanic reaction, how does E change at fixed temperature?
Відповідь
E decreases according to the Nernst equation. Le Châtelier's principle does not apply to an operating cell away from equilibrium; use Q and Nernst reasoning instead.
Картка 422
Питання
How are moles of electrons found from charge?
Відповідь
Moles e⁻ = q/F, where F ≈ 96485 C mol^-1 e⁻.
Картка 423
Питання
How does producing more gas particles usually affect system entropy?
Відповідь
It increases entropy because the particles have more positional microstates.
Картка 424
Питання
Can a dissolution with negative ΔH be unfavorable?
Відповідь
Yes. A sufficiently negative entropy change at the stated temperature can make ΔG positive.
Картка 425
Питання
When can a process with ΔH > 0 and ΔS > 0 become favorable?
Відповідь
At sufficiently high temperature, when TΔS exceeds ΔH.
Картка 426
Питання
How does a catalyst affect ΔG?
Відповідь
It does not change ΔG; it lowers the activation barrier for both directions.
Картка 427
Питання
For A → B, ΔGf°(A) = -50 kJ mol^-1 and ΔGf°(B) = -80 kJ mol^-1. What is ΔG°rxn?
Відповідь
-30 kJ mol^-1. Use ΣνΔGf°(products) − ΣνΔGf°(reactants) = -80 − (-50).
Картка 428
Питання
Why can dissolving a gas in a liquid have a negative entropy change?
Відповідь
Gas particles lose much of their translational freedom when confined and solvated in the liquid.
Картка 429
Питання
If coupled steps have ΔG values +20 kJ and -35 kJ, what is overall ΔG?
Відповідь
-15 kJ, so the combined process is thermodynamically favorable under those conditions.
Картка 430
Питання
What role does each half-cell solution play in an electrochemical cell?
Відповідь
It supplies dissolved redox species at an electrode interface and carries ions within its compartment. Separate compartments prevent direct mixing while the external circuit and salt bridge connect the half-cells.
Картка 431
Питання
How is E°cell found from standard reduction potentials?
Відповідь
E°cell = E°cathode − E°anode, using both tabulated values as reductions.
Картка 432
Питання
How does a cell's potential magnitude change as Q approaches or moves away from K, and what is E at equilibrium?
Відповідь
|E| falls toward zero as Q approaches K and grows as the system moves farther from equilibrium. At equilibrium, Q = K and E = 0.
Картка 433
Питання
How many moles of electrons pass when 1.93 × 10^5 C flows?
Відповідь
2.00 mol e⁻, from q/F.
Картка 434
Питання
How does a salt bridge maintain charge balance in a galvanic cell?
Відповідь
Anions migrate toward the anode compartment and cations toward the cathode compartment, countering the net charge imbalances created by the two half-reactions.
Картка 435
Питання
Why does raising a substance's temperature generally increase its entropy?
Відповідь
Energy spreads across more accessible particle energy states, increasing the number of possible microscopic arrangements.
Картка 436
Питання
When can a process with ΔH < 0 and ΔS < 0 be favorable?
Відповідь
At sufficiently low temperature, where the unfavorable -TΔS term is small.
Картка 437
Питання
Why can diamond persist even though graphite is more stable at standard conditions?
Відповідь
Conversion has a large activation barrier, so diamond is kinetically persistent.
Картка 438
Питання
What do the external circuit and measuring device do in an electrochemical cell?
Відповідь
The circuit carries electrons from anode to cathode; a voltmeter measures potential difference, while an ammeter in series measures current.
Картка 439
Питання
At constant temperature, how does increasing the volume available to a gas affect its entropy?
Відповідь
Entropy increases because the gas particles can occupy more positions in the larger space, so more microstates are accessible.
Картка 440
Питання
How does reversing one coupled reaction affect its ΔG?
Відповідь
It reverses the sign of that reaction's ΔG.
Картка 441
Питання
Why is n required in ΔG° = -nFE°?
Відповідь
It is the moles of electrons transferred per balanced reaction, linking charge flow to reaction extent.
Картка 442
Питання
What makes an electrolytic cell operate?
Відповідь
An external power source drives a thermodynamically unfavorable redox reaction; oxidation still occurs at the anode and reduction at the cathode.
Картка 443
Питання
In an Mⁿ⁺/M concentration cell, which half-cell is the anode: the dilute or concentrated ion solution?
Відповідь
The dilute half-cell. Oxidation produces Mⁿ⁺ there, while reduction consumes Mⁿ⁺ in the concentrated half-cell, so electrons flow from dilute to concentrated as the concentrations move toward equality.
Картка 444
Питання
How is deposited metal mass found from current and time?
Відповідь
Find q = It, convert q/F to moles e⁻, use the half-reaction ratio to moles metal, then multiply by molar mass.
Картка 445
Питання
Given product S° total 500 J mol^-1 K^-1 and reactant total 420 J mol^-1 K^-1, what is ΔS°?
Відповідь
+80 J mol^-1 K^-1.
Картка 446
Питання
How do electrode masses change in a Zn–Cu galvanic cell?
Відповідь
The Zn anode loses mass as Zn → Zn²⁺ + 2e⁻, while the Cu cathode gains mass as Cu²⁺ + 2e⁻ → Cu.
Картка 447
Питання
What is ΔG° when ΔH° = 50 kJ mol^-1, ΔS° = 0.200 kJ mol^-1 K^-1, and T = 300 K?
Відповідь
-10 kJ mol^-1, from ΔG° = 50 − (300)(0.200).
Картка 448
Питання
Why can temperature change a solid's solubility?
Відповідь
Temperature changes the balance of ΔH and TΔS, so it changes the free energy of dissolution and the equilibrium constant.
Картка 449
Питання
What does the size of ΔG° relative to RT imply about K?
Відповідь
ΔG° near zero gives K near 1. When |ΔG°| is much larger than RT, K is far from 1: negative ΔG° gives K ≫ 1, while positive ΔG° gives K ≪ 1.
Картка 450
Питання
Bubbles form at an inert cathode in acidic solution; which half-reaction can explain them?
Відповідь
2H⁺ + 2e⁻ → H₂(g). Gas evolution at the cathode can be direct evidence of reduction.
450 карток
AP Chemistry Flashcards: Complete 9-Unit Course Review
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